Gas blast fuse



Nov. 9, 1954 S. R. SMITH, JR

GAS BLAST FUSE Filed Sept. 2l, 1953 United States Patent O GAS BLASTFUSE Sidney- R. Smith, r., Stockbridge, Mass., assigner to GeneralAElectric Company, a corporation ofNeW York' Application September 21,1953, Serial N0..381,2;72'

2 Claims. Cl. 20G-120) This invention relates to a fuse,- and'moreparticularly, to a. fuse having a blast of gas directed across theelectrical arc.

Fuses having a blast of gas directed' against the electrical arc arewell known in the art. One form of such a fusev comprises a fuseA tubeclosed' at one'endand: openI at the other end. Within the. fuse tube ispositioned a fuse link having a fusible portion. Adjacent the closed endof thev fuse tube is positioned a cartridge of compressed gas. Theinterior walls of the fuse tube are constructed out of or' lined with amaterial which will evolve a gas when subjected to an electrical arc.When an overcurrent occurs in thev fuse link, the fusible portion willmelt or rupture. The resultant electrical arc will cause the interiorside walls of the fuse tube to evolve a gas which will aid inextinguishingV the electrical arc. Simultaneously', the electrical arcor the hea-t thereof will puncture the gas cartridge whereuponadditional gas will be present in the fuse tube to extinguish theelectrical arc. In such` a fuse the quantity of gas evolved by theinterior side wal-ls of the fuse tube is very large and also very highpressures are built up within the fuse tube. Accordingly, the fuse tubemust be constructed to withstand the4 forces of this large quantity ofgas and its high pressures.

When a fuse of the type just described is used in a cutout, as the opentype cutout wherein the fuse tube is` positioned adjacent to andvmounted on an elongated insulator, the gases produced within the fusetube are expelled out of the open end of the fuse tube. This eXpulsiveaction of the gases out of the open end of the tube imposes high recoilforces upon the fuse tube and said recoil forces are transmitted to theinsulator which carries. the fuse tube. Since the insulator has alimited strength and withstands recoil forces only of apredeterminedvalue, the current interrupting ability of the cutout is accordinglylimited.

It is an object of this invention to provide a gas blast fuse whereinthe quantity of gas within the fuse tube and the pressures built upwithin the fuse tube can. be substantially predetermined and controlled.

My invention comprises a gas blast fuse having a fuse tube closed at oneend thereof and open at the other end thereof, a fuse link having afusible portion positioned within said fuse tube, a cartridge ofcompressed dielectric gas positioned within said fuse tube, the interiorside walls of said fuse tube constructed out of a material which willevolve substantially no gases when subjected to an electrical arcwhereby the quantity of gases within said fuse tube and the pressureswithin said fuse tube upon fusing of said fuse fusible portion can besubstantially predetermined and controlled.

The invention will be better understood by considering the followingdescription taken in connection with the accompanying drawing and itsscope will be pointed out in the appended claims.

In the drawing, Fig. l is a side view, partly in section, of one form ofmy invention. Fig. 2 is a detailed side View, partly in section, of theupper portion of the fuse tube shown within Fig. 1. Fig. 3 is a detailedside view, partly in section, of an upper portion of a fuse tubeillustrating another 'form of my invention. Like reference numeralsthroughout the various figures are used to indicate similar Darts.

L Referring now to the drawing and more particularly to Fig. l, showntherein is an open type cutout having an elongated porcelain or otherinsulating material member 1. The insulator 1 is carried by a pole lineor the like from a support arm 2. Mounted adjacent the upper end portion2,694,123 Patented Nov. 9, 1954 of the insulator 1 is terminal contacthardware comprising a U-shaped resilient latchcontact portion 3 and' aline terminal connecting portion 4. Connected adjacent the lower endportion of the insulator 1 terminali Contact hardware. comprising ahinge Contact portion 5 andi a line terminal connecting portion 6.

A fuse tube 7 having` circuit interrupting means therein spans andelectrically connects the upper terminal contact hardware and the lowerterminal contact hardware. The fuse tube 7 is closed at its upper endlandi open at its lower end. Fuse tube 7 is pivoted at its lower end tothe lower terminal contact hardware by a toggley mechanism comprisingl aclamping member 9- and a generally l.shaped contact 1li. Contact 10ispivoted' at one of itsl ends tothe clamp 9 and pivoted atits otherend' to the hinge element 5. Within the fuse tube 7 is positioned a fuselink 8 which extends out of the open lower end of fuse tube 7 and istautly fastened to the contact 1G whereby the lower end of the fusetubev 7 will abut the Contact As will be obvious to those skilledintheart, when the fuse 11i-nk 8 is ruptured the fuse tube 7 will movedownwardlyv and pivot away from the contact iti: Simultaneously, thecontact 1i) will pivot away from the hinge S whereupon the fuse tube 7will be unlatched from latch 3 for drop out movement;

Conventionally, the interior4 side walls of the fuse tube 7` have beenconstructed out of or lined with a material which will' produce adielectric gas wheny subjected to an electrical are. Accordingly, whenthe Euse link 3 is ruptured and an electrical arc is drawn between thebroken ends thereof, said electrical arc or the heat thereof will causethe interior Walls of the fuse tube 7 to evolve a gas. Said gas aids inextinguishing the electrical arc and is expelled out of the openbottoneA end of fuse tube 7i This expulsive action causes the fuse tube7 to recoil axially upward. Therecoil forces imposed on fuse tube 7 aretransmitted to insulator 1 through the upper and lower terminal contacthardware, and the recoil force imposed on the insulator 1 tend tofracture it thereby limiting the current interrupting capacity of thecutout.

Referringy now to Fig. 2, shown therein is a detailed side View of mygas blast fuse. in my invention the fuse tube 7 is constructed out of arefractory or inert material. That is, fuse tube 7 is constructed out ofan insulating material which will produce substantially no gases whensubjected to an electrical arc or the heat thereof. For in stance, fusetube 7 can be constructed out of porcelain, micalex, steatite, or otherlike materials.

Positioned on the upper end of fuse tube '7 and c onnected thereto is acylindrical Contact member 11. Member 1 1 has a central innercylindrical flange 1 2 formed therein between itsy opposite ends.Contact member 11 can be fastened to the upper end of fuse tube 7V as bythreads or the like whereby the flange 172v willv abut the uppermostedges of fuse tube 7. Within the upper end of fuse tube 7 is positioneda cylindrical gas cartridge support 13 carrying a cartridge 16 ofcompressed dielectric gas. Gas cartridge support 13 has a frusturn-likeportion 14 at the lower end thereof and at its upper end support 13 hasan outer flange 15. Flange 15 rests upon and is in electrical contactwith liange 12. Gas cartridge 16 is supported and accurately positionedby support 13 as by a circumferential groove or indentation 17 incartridge 16 and an internal circumferentially extending bead 18 wherebythe gas within the cartridge 16 will be accurately blasted across theelectrical arc.

The upper end of fuse tube 7 is closed by a contact cap 19 which threadsdown into the contact 11 to force the ange 15 into intimate electricalcontact with flange 12 or contact 11. Fuse link 8 is connected to thefrustum-like portion by a fuse link fusible portion 20 and strain wires21. The lower or nipple end of the gas cartridge 16 is closed by a thinseal or disk 22 of fusible metal.

As will be obvious to those skilled in the art, when an overcurrentoccurs in the fuse link 8 the fusible portion 20 and strain wires 21will fuse or melt. Substantially simultaneously therewith the electricalarc or the heat thereof will cause the seal 22 of gas cartridge 16 to bepunctured. Accordingly, the compressed gas with- 3 in gas cartridge 16is now released to be blasted across the electrical arc within the fusetube 7.

In my invention I prefer to use sulphur hexauoride gas within the gascartridge 16. This is because sulphur hexafluoride has good dielectricand heat removal characteristics and will effectively cool andextinguish electrical arcs. However, it is obvious that other dielectricgases can be used within cartridge 16. For instance, carbon dioxide canbe used as the gas employed to put out the arc.

It will now be apparent that in my invention the amount of gas generatedwithin the fuse tube 7 and the gas pressures built up within the fusetube 7 can be accurately predetermined and controlled. Substantially nogases are evolved by the interior side walls of the fuse tube 7 and thegases used to snuff out the electrical arc are contained solely withingas cartridge 16. Further, the gas cartridge 1.6 is accuratelypositioned within fuse tube 7 whereby the gases within cartridge 16 willbe blasted substantially directly across the electrical arc within thefuse tube 7. With the volume of gas produced within fuse tube 7 and thegas pressure within fuse tube 7 substantially controlled, the fuse tube7 need not be made as structurally strong as in conventional gas blastfuses. Accordingly, the costs of my fuse has been substantially reducedover the costs of conventional fuses. The amount of gas within cartridge16 is preferably just suficient to scavenge the fuse tube 7 and snufl;`out the electrical arc therein. With a decrease in the volume of gas andthe gas pressures employed to extinguish the electrical arc within thefuse tube, smaller recoil forces are imposed on the fuse tube 7.Consequently, smaller recoil forces are transmitted to and imposed uponthe insulator 1 of Fig. 1 when my fuse is used in a cutout.

Therefore, cutouts employing my gas blast fuse can have a higher currentinterrupting capacity.

Referring now to Fig. 3, shown therein is another embodiment of myinvention wherein the gas cartridge support means is less complicatedthan the gas cartridge support means of Fig. 2. In Fig. 3 the gascartridge support means comprises a circular plate or disk 23 having acentral opening and tabs 24 formed therein. The tabs 24 are disposedwith respect to each other in a frusturn-like arrangement and the vertexof said frustumlike arrangement is directed towards the open bottom endof the fuse tube. The gas cartridge has a frustum-like lower end portionwhich is disposed within said frustrum-like arranged tabs 24. Otherwise,the construction and operation of the gas blast fuse of Fig. 3 issimilar to the construction and operation of the gas blast fuse shown indetail in Fig. 2.

While there have been shown and described particular embodiments of theinvention, it will be obvious to those skilled in the art that changesand modifications may be made without departing from the invention andthat it is intended by the appended claims to cover all such changes andmodifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A fuse comprising a tube closed at one end thereof and open at theother end thereof, a fuse link having a fusible portion within saidtube, said fusible portion fusing in response to an overcurrent in saidfuse link whereby an electrical arc is established between fused ends ofsaid fuse link, means for introducing a predetermined quantity ofsulphur hexauoride gas at a predetermined pressure within said tube toextinguish said electrical arc, said means comprising a cartridge ofsulphur hexafluoride gas within said tubular member, said gas releasablefrom said cartridge in response to establishment of said electrical arcWithin said tube, said sulphur hexafluoride gas blasted across saidelectrical arc to extinguish said arc, the interior walls of said tubeevolving substantially no gases when subjected to said electrical arc orthe heat thereof.

2. A fuse comprising a dielectric non-gas evolving tube having a fuselink positioned therein; said fuse link consisting only of a flexiblemetallic conductor, at least one metallic strain wire and one metallicfusible portion, and a metallic cylindrical gas cartridge retainingmember having an integral metallic frustum-like part at one endmostportion thereof and an integral metallic annular outer flange at theother endmost portion thereof; one end of said flexible conductorconnected to said part by said strain wire and fusible portion, theother end of said flexible conductor extending out of one end of saidtube, a metallic cylindrical internally threaded collar having an innerintegral metallic annular shoulder therein approximately centrallythereof, the other end of said tube being externally threaded, saidinternally threaded collar threadably engaged at one end thereof withsaid externally threaded tube end whereby the endmost edge of saidthreaded tube end is in engagement with on side of said shoulder, anexternally threaded metallic cylindrical closure cap closed at one endthereof threadably engaged at the other end thereof with another end ofsaid internally threaded collar, said flange engaged with another sideof said shoulder and clamped between said shoulder and the endmost edgeof said closure cap other end, a closed metallic cylindrical cartridgeof compressed sulphur hexauoride gas, said cartridge having acircumferentially extending indentation formed in a central portionthereof, said flange having a peripherally extending integral metallicbead formed along the inner perimeter thereof, said cartridge disposedwithin said retaining member and said bead engaged with saidindentation, the end of said cartridge remote from said closure caphaving a metallic nozzle-like integral part disposed concentricallywithin said frustum-like part, said nozzle-like part closed by fusiblemetal.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,952,734 Ten Brook Mar. 27, 1934 2,429,518 Kyle, Jr., et al.Oct. 2l, 1947

